Automatic switchboard telephone system



April 10, 1928. 1,665,773

L. L. E. CHAUVEAU AUTOMATIC SWITCHBOARD TELEPHONE SYSTEM Filed Feb. 7, 1924 4 Sheets-Sheet 1 April 10, 1928. 1,665,773 1 L. L. E. CHAUVEAU AUTOMATIC SWITCHBOARD TELEPHONE SYSTEM Filed Feb. '7, 1924 4 Sheets$heet 2 If q .5 c I u:

Invenibr L.L.E.Chawzraau April 10, 1928.

L. E. CHAUVEAU AUTOMATIC SWITCHBOARD TELEPHONE SYSTEM 4 Sheets-Sheet 3 Filed Feb. '7. 1924 121 EVlEQ I-mrenTor L-L-E- Chduveau April 10, 1928.

1,665,773 L. L. E. CHAUVEAU AUTOMATIC SWITCHBOARD TELEPHONE SYSTEM Filed Feb. 7, 1924 4 Sheets-Sheet 4 Patented Apr. 10, 1928.

UNITED STATES LOUIS LUCIEN EUGENE CHAUVEAU, 0F PARIS, FRANCE.

AUTOMATIC SWITCHBOARD TELEPHONE SYSTEM.

Application filed February 7, 1924, Serial No. 691,310, and in France May 5, 1923.

The present invention relates to improvements in telephony with an automatic central switchboard, as set forth in the presentspecification, and illustrated in the accompanying drawing, in which:

Figures 1, 2, and 1 taken together with Figs. 1 and 2 arranged side by side with Fig. l to the left, Fig. 3 placed below Fig. l. and Fig. 4 placed. below Fig. 2, represent a general diagram oi the invention.

In the drawing-the movable contacts of the relays are illustrated as in the inoperative state, their operative position being that in which these contracts are near the coils.

The elements composing the automatic switchboard telephone system herein described may be divided into live groups:

. The station elements.

The line elements.

The connecting elements.

The commutator elements. The signal and manipulating elements.

Stations, Af -C T e stations comprising the system are subdivided into a certain number of groups, which number is equal to the square root of the number of stations, if this square root is a whole number, but if the number of groups is equal to the whole number immediately higher than the square root of the num ber of stations, there will be, for example, three groups of 3 stations, four groups of 4 stations, five groups of 5 stations, etc.

Each station comprises: a polarized call signal S. a condenser C, an induction coil 11 a receiver R and a microphone M. These members may be mounted according to any o the numerous arrangements used for this purpose.

In addition, each station is provided with a call plate connected to a test relay.

The call plate is iormed ot a control wheel RC. which may rotate on its axis operating the impulse wheel RI; these two wheels are rigidly connected. and coupled together, as shown on the drawing. They may be manipulated manually and are returned in the opposite direction by the action of a spring, the position of the assemblage in inoperative state being that illustrated on the drawing.

The test relay T interposed in the line, and the latter is cut by the commutator hook 6 when the receiver is hooked up; when the latter is unhooked the line is closed at 7.

The test relay is provided with an armature 5, constructed to rotate with heavy friction so that it remains in the last position in which it has been carried; in the inoperative position the armature is raised by the commutator hook and, by means of its tip, which forms a stop, prevents the wheel from rotating, remaining in this position until actuated by the test relay.

In the position of rest and when the dial is turned in the direction indicated by an arrow, the contact remains closed.

hen the dial turns in the opposite direction, the abutment stops the member A; the member B rotates around X and the contact- 11 is opened.

hen the station is called, the vibrated calling ciu-rent passes through the condenser C and the bell S. Although the contact 11 is closed (its position of rest) the receiver R is hooked and the contact 7 is open. It is obvious that it the receiver is unhooked at the moment of the call, thev calling current then also passes through the primary coil I; (through the contact 7) and a sound is heard in the receiver. This arrangement oft the calling system is otherwise generally employed in installations of this kind.

The system is therefore operating when the contact 11 is closed.

In tho inoperative state the test relay T short circuited by the contact 4, and the wheel RC may be madeto break this contact by means of the tooth (Z, the relay T then being in line if the hook commutator has been unhooked. If at this moment a current passes through the line the test relay attracts its armature 5, which is released, permitting the passage of the tooth d of the wheel BC. The test relay is again short circuited.

The tooth (Z of the wheel RC may carry along the cam 10 and open the corresponding contact when the wheel turns in the. direction of the arrow F, which cuts the short circuit of the test relay. The tooth (Z closes this contact when the wheel rotates in the opposite direction and thus re-establishes the short circuit. I

The control wheel RC has a certain number of openings each corresponding to one of the figures forming the number of the stations of the system. The impulse wheel RI has a certain number of teeth corresponding respectively to each of the openings of the control wheel RC; these teeth move before a contact 11, normally closed, but which they open when the wheel rotatesin a direction reverse to that indicated by the arrow F, this contact being t. course, arranged so that it can not be opened when the wheels rotate in the direction of the arrow F.

The speed of the return movement of the wheels, under the action of a spring, is subject to the action of a butler, so that the openings of contact 11 are reproduced at predetermined and properly spaced periods.

The position of the cam is such that, during the movement of the wheels in the direction opposite the arrow F, the contact 10 may be closed during the last opening of contact 11, so that the test relay T is short circnited during the last closure of 11. Summarizing, the above described assemblage comprises an ordinary telephone station provided with a call plate adapted to cut the line a certain number of times. A test relay is interposed therein, and it is necessary that this relay be excited to release the call plate and, hence, permit a call.

In addition, the winding of the test relay T forms a resistance which is interposed in the circuit when contact 11 is cut. The station is thus capable of controlling, over its Lines (L1G).

The stations are connected with the automatic switchboard by the lines, each of which is represented on the switchboard by three relays:

1. The line'relay A.

2. The feed relay D.

3. The coupling relay CP.

The line relay A serves to connect the line with the commutator (COP) through the contact Therelay A receives current through the line when the subscriber unhooks his apparatus. The relay A is provided wit-ha guard contact 61.

The guard. protective or maintenance contacts of relay A of all the stations are mounted in series, so that when the relay A of station 1 functions the guard contact of the other stations is not fed, the result thereof being that in case of a simultaneous call of several stations only one of the relays A is excited, which is that nearest No. 1. The station 1 thus has priority over station 2 and the others, the latter having priority over stat-ions 3 and the others, and so on.

The feed relay D likewise has its circuit closed by the line and the station which it station.

feeds during conversation. When inoperative this relay is not fed, but may be supplied by the contact 13 of one of the relay pins F when one of the latter functions. In this case the relay Dis protected by its contact 18 untilthe subscriber hooks up. \Vhen excited, the feed relay 1), by means of its contact 15, cuts the circuit of the call relay A and, by means of this same contact, closes the circuit of the relay pins F of the station, as explained hereinafter. By means of its contact 17 the relay D switches the selective line to the line Busy PL.

The connecting or coupling relay CP may be excited either by the selective line 35 of the station, contact 17 being inoperative, or by the line CA and the contact 16 of the relay A, when the latter functions, that is to say, when the station is calling. The excited coupling relay CP,by means of its contact 14, connects the working coil 21 of the relay F' to one of the poles of the battery and interrupts the short circuit at 20 of a part of the coil of the feed relay D. Relay Cl thus controls the relay F.

Connections (URI 0R2 R-.1). I

These are the assemblage of. elements serving to connect the stations with each other,

Each connection comprises: 7

1. As many pin or switch relays F as there are stations in the system.

2. A signal relay G.

3. A connecting relay H.

4. A connection transfer relay PH.

The relays F are provided with a working coil 21 and a protective guard or maintenance winding 22, the function of which is to connect, through contacts 26, the line corresponding with the two conductors C1 and C2, so that two stations may be connected together by the conductors C1 and C2 when the two relays F of these two stations, on a same connecting line, are excited.

The entrance terminal of the working coils 21 of all the relays F of one stat-ion may be connected with one of the poles of the bat tcryby means of the contacts 14- ot the coup ling relay CP of this station. The exit of the working coils of the relays (F) oi the same connection is connected with the other pole of the battery thru the signal relay G. However, at any one moment, there need be but a single connection connected to this latter pole of the battery, by reason of the action of the electromagnetic connection transfor elements PH. Consequently, when a request is made for connection, it is the connection whose relays are connected with this latter pole which is utilized. The coil ol the relays F is connected with one of the poles of the battery by means of the contact 15 of the feed relay D of the corresponding It is connected to the other pole of the battery through the connection relay H.

The signal relay G is mounted in series on the common return winding of all the coils 21 of the relays F of its connection; it is excited when one of these working coils (21) is excited. By means of its contacts 25, the relay G connects the line with the signal circuit formed by the two wires A1. A2 terminating at the call vibrator. By means of its contact 27 it is protected, as ex' plained hereinafter. Finally, by means of its contact 28, itcontrols the electromagnet U, which actuates the call and signal elements.

The connecting relay H is mounted in series with the guard or maintenance coils 22 of the relays F of the same connection or line; by means of its contact 29 and 30, it prepares the circuits of the electromagnet PH of the same line, so that these may be excited immediately after the action of the call or signaling members.

The purpose of the relay transfer of connection PH is, when its line is occupied, to pass the hole of the battery to the connection following by means of the 'contact 36, so that the said successive connection may be used for a new call.

The relay PH comprises a working 'coil 32 and a protective coil 33. Current is passed through the coil 32 at the end of the action of the call members and is retained by its contact 34 and the contact 30 of H until this latter comes to rest, that is to say, until the two busy stations have hooked up again.

Current is passed through the coil 33, by means of the contact 38 and the line 13, during the time in which the calls come in when the corresponding connecting line is busy, so that, even if the busy stations hook up, the line is not free until the end of the call. so as not to cause any disturbance on the line. The relay PH, by its contact 57, holds (protects) the circuit of the relay H of the same connecting line.

Oomwmzator COP) The commutator operator is formed of two groups of elements:

The first of these groups is the automatic commutator proper; it comprises:

1. The operating relay Mn.

2. The time relay 1T.

3. The second time relay 2T.

at. The time change relay 4T.

5. The successive engaging relays C1- C2C3Cn.

6. The zero relay 0.

This assemblage is arranged in such manner that under the action of the successive impulses received by the working relay M11,

the relays C1 to C4 are successively connected in proportion to the degree or extent in which these impulses come in.

For this purpose the operating relay Mn pass current alternately, in proportion to the extent at which the impulses come in, through the uneven and even line.

The relays C1, C3, C5, etc., are connected to the Uneven line, while the relays C2, C-t are connected to the Even line, but this is not a direct connection. the relay C2 being connected to the Even line through contact 112 of relay C1, relay C3 being connected to the Uneven line through the contact 112 of the relay C2, and so on.

The details of operation of this automatic commutator will be more easily understood by referring to the part of this specification relating to the operation hereinafter set forth.

The relay C1 functions during the first impulse and its purpose is to connect the line LA with the line LE by means of its contact 113.

The relay C2 functions during the second impulse and serves to connect the line LB with the line LE through its contact 113, while, through its contact .114, it cuts the connection LA-LE established by C1.

The relay C3 functions during the third impulse and connects the line LC with the line LE by means of its contact 113 while, by means of its contact 114, it cuts the connect-ion LB-LE established by C2.

The relay C4 connects the line LD with LE, while it cuts LCLE, and so on.

The relay 0, through its contact 110, cuts the return of all the electromagnets of the commutator.

It is thus evident that the arrival of impulses results in connecting successively with the line LE, the lines LA, LB, LC, etc, the last line connected in during the last impulse received remaining connected only to LE.

The stations of the system being distributed as set forth in the (.lescriptiou thereof, the function of the automatic coimnutator is: (1) to find the group to which the station called belongs; (2) to find in this group the station called and connect it with a free line. The number of relays C1, C2, C4 may thus be equal to that of the groups.

The second group of members of the commutator COP comprises:

1. The group coupling relays CGA CGB CGC, etc.

The The The The The ordinator relay I.

impulse relay 2'.

auxiliary impulse relay i. armament relay ARR l. commutator control relay J. The group pilot relay P.

The transfer relay K.

9. The auxiliary transfer relay K. 10. The pre-zero relay PZ.

11. The zero relay Z.

s r s sw s r The relay connections of group GGl, (1G2, CG3, etc. are controlled by the lines LA, LB, LC, etc. and the object of which is to connect all the stations of the same group with the automatic commutator.

There is thus one relay coupler p r group of stations. Each relay coupler has as many contacts as there are stations in its group, each contact controlling the connecting relay CI of the corresponding station. In addition, the coupler relay has a protective locking contact 36, which keeps it excited as soon as it receives an impulse, until the connnutator operator resets to zero.

The ordinator relay I and the impulse relay '5 are interposed in the circuit of the line LI, which circuit is normally closed by the calling station, when this latter is connected with the commutator operator by. its line A relay.

The sensitiveness of relays I and z ditlers, their adjustmentbeing such that when the resistance of the test T of the calling station short circuited, the two relays tunction and establish the working contacts 39 and 40. If the short circuit of the test relay is interrupted after operation oi the two relays, these latter remain adhering.

When the circuit is connected by means of the impulse wheel RI at 11, the two relays I and i are inoperative and return to their normal position. Finally, the two relays being inoperative, it the circuit is closed without the resistance of the test T being short circuited, only relay 6 functions.

lVe thus have a selective system ot' two signals of different intensity, the relay r11, operatingrt'or a weak intensity, act-s under the impulses of the call plate and controls the operating relay Mn through its contact 39, while the relay I acts at the end of the series of impulses to pass currentthrough the line LE by its contact 40, that'is to say, to pass current through one of the lines LA LB LC LD, according to the position of the relays C1 to On.

In order to utilize the present connnercial type of call plate, use may be made of the control by short and. long impulses; in this case the impulse relay only is interposed in the line LI, this relay then being of the ordinary type. I

The ordinator relay I is ot a ditlercnt type, that is to say that it closes its contacts with a certain delay. This relay is controlled by a contact of i and one ot the relay Cl. so as to be excited only when Cl is connected in and i itself excited for a certain period of time; this occurs at the moment in which the call plate comes into a position of restafter a series of impulses. This method of selection is not comprised in the following description being mentioned solely to describe the selection by currents of different intensities.

The auxiliary impulse relay i is controlled by the contact of relay .5 and controls, through its contacts, various auxiliary functions, as set forth hereinafter. I I y The armament relay ARM, controlled by the contact 71 of i, operates as soon as, a station is connected with the commutator operator; it has a contact l2? which maintains it excited for the entire duration of the impulses. By means of its contact 1528 .it causes the operating relay Mn to pass-under the control of the contact 39 of the impulserelay 2', so that Ma operates each time the call plateRI of the subscribercuts the line through the contact 11. V y

The commutator control relay .J, con trolled by the contact 114 of C1, isexcited as soon as the latter functions until relay comes into action. By means of its contact 4-2 it controls the electromagnet K in such manner that the latter can not function before the automatic commutator has been brought to the inoperative state after the first series of impulses. p i

The group pilot relay 1 is interposed in the guard (or maintenance)- circnit of the electromagnet group connect-ions 0G1, 0G2, 0G3, etc. It functions at the same time as one of these and, through its contact 46, controls the electromagnet O, that is to say, the return to normal of the automatic commutator. Through its contactt lthe electromagnet 1 controls the relay K, so that when J is at rest, that is, when the commutator has been brought to zero after the first series of impulses, relay K is energized.

The transfer or. change over relay K functionsafter the first series of impulses, as has just been described. Through its contact 43 it controls the auxiliary transfer relay K, which connects the lines LA LB LG to the'lines N1 N2 N3, etc, so as to direct the second seriesof impulses to the :alled station when the relays of group CGl CGQ etc. are excited. i

It is thus apparent that the combination of elements of the switching mechanism GOP is such that at the end of the first series of impulses one of the group connecting relays is and remains energized. The pilot relay P, in controlling 0, causes the comnmtator to return to zero. Then the change over relay K operates so that at the end of the second series of impulsescurrent is passed through the selective line 35 of the station called and,- hence, the coupling electro GP of this station operates.

The pro-zero relay PZ, at the end. of the action of the commutator, is controlled by the relay L, as explained hereinafter, The relay PZ, through its contact partially closes the circuit ol the general zero relay Z.

The Zero relay Ztnnctions when'thc calling station is cut oil from the commutator, contact 71v of i returning to normal.

The relay Z cuts all the circuits of the commutator relays, either directly through its contacts 77 and 48 or by controlling the action of the relay 0 through the action of relay 7.

Signals and operations SMA.

The groups of signal and operation elements comprises:

1. The interrupter relay Q.

2. The interrupter relays Q1, Q2, Q3, etc. 3. The auxiliary interrupter relay Q. 4. The line relay AC.

5. The call relay U.

6. The answer relay R.

7. The call train MA.

8. The first position relay M1.

9. The second position relay M2.

10. The signal relay X.

11. The auxiliary signal relay \V.

12. The third position relay M3.

13. The auxiliary call relay U.

14. The line interrupter relay CD.

15. The control relay L.

The function of the interrupter relay Q is, by means of its contact li), to close the interrupted relays Q1 Q2 Q3, etc., which break the connection of cach call relay A with the line of each subscriber, so as to prevent calling while the interrupter relay Q is energized.

The relay Q may be excited either by the contact 50 of the auxiliary interrupter of the circuit Q, or by the line LQ. The relay Q being energized during the entire activity of the commutator and the line LQ being under current thru contact 123 of U or contact 56 of V, during the operation of the signal and operating elements, the result is that no call can come in while the automatic switchboard is busy.

The stations are provided for this contingency, since they are cut oil' from the bat tery by the contacts 51 of Q1 Q2 Q3 and, consequently, their test relays T do not function.

In addition, through the contact 49 of this same relay Q and by the contact 57 of AC. the locking coils of the transfer relays PH are energized in such manner that if the busy stations hang up while another station is calling the line used by the busy stations is not released until the end of the call, so as to avoid disturbance.

The busy line relay AC is controlled by the contacts 36 of the relay PH, and, it in turn controls the relay Q in such manner that when all the lines are occupied a call can not come to the switchboard while a line is not free.

The call relay U is controlled by the con tact 28 of the signal relays G; through its contact 115 it operates the call mechanism MA, and through its contact 117, the call. buzzer or vibrator ViB.

The mechanism MA is of any type ordinarily used for lighting fixtures, and may be adjusted to operate for the time considered necessary during a call; it is combined with the first position relay M1, with the second position relay and with the third position relay M3 in such manner that:

1. During the first operation (normal call) it closes the contact 53 and controls MI. The latter is then held at 93, 94 breaks at the circuit of MA, whose core descends slowly. If the station called replies the line PL is placed under current and, through 95 in operation, the answer electro It is placed under current and cuts the circuit of U at 120, which stops the vibrator.

2. During the second operation (no answer) at the end of the period corresponding to the first operation, the contact 58 is closed which, through 96 of M1, actuates X and \V, this latter connecting in, through its contacts 5:), a potentiometer between the lines A1 and A2 and the vibrator to reduce the call current; X, through its contact 57 again energizes the call mechanism which rises, 53 is again closed, which actuates the second position relay M2; the latter breaks, at 19, the circuit M1 which returns to normal; 95 then connects the line PL with the contact 52 of X; M2, by its contact 24, interrupts the mechanism MA, the core of which begins to descend and close 59, which actuatcs the third position relay M3; at the.

end oil? the second period of travel of the mechanism 58 is again closed, M2 exciting 98 and the line breaking relay CD is energized.

Summarizing, the action of the mechanism MA and of the relays M1 M2 X and WV is such that, during an ordinary call the vibrator is connected directly to the lines A1 A2, that is to say, to the connecting line in use, while in case of no answer this connection takes place through a potentiometer. More over, it will be seen from the description of the operation given hereinafter that in case of Busy or \Vrong number, the line relays X N and M2 function immediately, the operation being the same as with no answer, the signal being the same in all cases. This combination permits of using but one mechanism.

The third position relay M3 controlled by the mechanism MA, as stated above, is held by its contact 126 and, at 125, breaks the cir-v cuit of the signal relay G, said circuit comprising the resistance R and controlled by the contact 54 of X. g

The auxiliary call relay U operates at the same time as U and, through 123, keeps the interruptor relay Q energized during the entire period of the call; at 122 it closes the circuit controlling the line transfer electros PH. The relay U differs slightly, in that \22 may be closed shortly after U has come to normal, and that the line may not be changed or transferred except when the entire assemblage is at rest.

y The connection line interrupting relay CD is controlled b the train MA at the end of its travel, if 2 is energized, that is to say, if there is no answer or busy signal; CD, at 124, breaks the connection on which the signal has been given, so as to release the line, even if the caller has not hooked up.

The switch control relay L functions at the end of the operation of the switching mechanism GOP and, through its cont-act 4C5, actuates the pre-zero relay 'PZ. In addition, through its contact 81, it releases the Busy signal, if the number asked for is greater than the number of stations comprised in the system, as will be explained hereinafter.

In addition to the above named elements, the Signal and operating group coniprises the \Vrong number elements, which are:

1. The fault instrument M11.

2. Its control relay FA.

3. Its interruptor relay FB.

4. The auxiliary Fault relay FC.

The object of this assemblage is, in case 01 error, to cause the commutator to be ire-set to zero and to send a signal to the station making the error, if the caller has not already hooked it The l ault control relay, controlled by 89 of 11, through its contact 85, actuates the mechanism or train (wrong number train) The interrupter relay F13, controlled by the contact 82 of the train MF, breaks the circuit thereof at 83.

The mechanism MF, which is actuated as soon as a station is connected with the switching mechanism GOP, is so regulated that it can not close the contact 80, in its descent, except at the end of an interval. of time much longer than that necessary to call a station, so that at the end of this period, if the caller has not been connected with the number of one of the stations of the system, the relay PZ is excited and the switching mechanism is returned to normal, if the sub scriber has hung up, while the signal relay X and its auxiliary IV, are energized if the caller has not hung up.

OPERATION.

To facilitate understanding the operation of the assemblage, the latter is set forth insimultaneous conversations, are assumed as free.

A4- removes his receiver R and, closes the line at 7 the latter receives current from the positive through the contacts 20 of D and 20 of GP. It connected on the other side to its call relay A by one of the contacts 51 of Q1, A being connected to negative by the contact 15 of I). v

The wall relay A of station A1 functions and, bymeans of its contact 00, connects the line L1 with the station. The latter being always connected to the positive through and .20, the relay operates and controls i, the contact 72 is closed, which actuates relay Q, which remains in operation and energizes the relay Q. The latter, in turn, actuates the relays Q1 Q2 Q3 etc. All the stations are thus cut olf'from their call relays A; no other calls can come to the switchboard, the stations being provided for this contingency by the non-operatiim of their test relays.

However, the call relay A of station A 1; remains energized, being kept so through its contact (51, and station At may thus control the relays i and I.

If several stations have called simultaneousl y, since the contacts 61 are arranged in series, only the station nearest Al, the original of the series, will. remain locked. It is seen, for example, that contact 61 of A lcuts the positive feed current of contact 61 of B,.

The auxiliary impulse relay 1 operating, has, by means of its contact 71, closed the circuit of the armament electro ARM, which is held at 127 and partially closes, at 128, the circuit of the operating relay hale.

The caller turns his all plate or dial to call station C1 and carries the letter C along the arrow F in its return movement, the wheel R1 opens the contact 11 three times, the impulse relay i returns to rest three times and, through its contact 39, closes the circuit of the operating relay Mn three times.

At the lirst impulse Mn, through its operating contact 101, and the inoperative con tact 107, passes current through the uneven or odd line. At the same time, by means of operative contact 100 and inoperative con-' tact 109, the relay 1T is energized and is maintained so by its contact 102. This relay 1 T, through 104-, partially closes the circuit of the relay 2T.

After the first impuse lvin returns'to rest, The relay 2T is then energized by contact 101 and contact 10 1. Contact 10? comes to the operating position, and relay 2T is main tained actuated byits contact 105. At the second impulse current is passed through the Even line through 101 and lOi in operation. At the same time, through 101 and 106, at rest, the electro LT is energized and,

loo

at 109, breaks the circuit of 1T, the latter returning to normahbut 2T remains excited by means of the contact 108 of 1T.

After the second impulse 1T returns to normal, 108 being open, 2T likewise comes to rest. The relays 1T QT and etT are then in the position which they occupied before the first impulse.

At the third impulse the cycle is repeate, as during the first impulse.

It is thus apparent that the combination of relays Ma, 1T, QT and LT have the efi'fect' of alternately passing current through the lines Uneven and Even in proportion to the receipt of impulses transmitted to Mn through the impulse relay During the first impulse therelay C1 connected to the Uneven line operates and is maintained by its vcontact 111 isolated, by this same contact, on the line Uneven. The relay C1, through its contact 113 and the Contact 114 of G2 at rest, connect the line LA with the line LE. This is the selection of the first impulse. At the same time, tl'irough its contact 112, C1 connects C2 to the Even line. Finally, through its coutact 1H, C1 actuates the control relay J.

At the second impulse, the Even line being under current, C2 will operate, is maintained thu by its contact 111, and isolated by this same contact. G2, at 11 1, breaks the connection LA and LE, which thus nnllities the tirst impulse. C2, through its contact 113 and by the contact 114 of G3 at rest, connects the line LB with LE. This is the selection ot the second impulse. C2, through its contact 112, connects the relay G3 with the Uneven line.

At the third impulse C3 operates and connects the line LC with LE, while breaking LIE-LE.

it is thus seen that the relays C1 to C4: successively engage in proportions as the -=is are received, the reception of three suc assive impulses resulting in establishing the connection LC-LE.

But, after the third impulse, the wheel {1 of the call dial or plate of the calling tation has closed the contact 10, which short circuits the test relay T. The order relay 1 is then excited at the same time as is the impulse 2', and contacts 39 and 40 are operatire; the line LE is connected to the negative pole of the battery through the resistance RP. Since, at this moment, LE is connected with LC, the relay of group CG3 energized, since the relay K is normal; the coupling relay of group CG3 operates and connects the selective lines 35 of the tour posts C1 to C 1- respectively with the lines N to N4. The selection of the group requested thus efiected.

in operating, the relay CG3 has closed its retaining contact 88, which actuates the pilot electrode P, the purpose of the resistance RP being to maintain a certain difference of potential between the entrance terminal of CG3 and the negative pole, in order that P may function. 7

At (36, the pilot relay P closes the circuit of the relay 0, and at 4 1, closes partially the circuit of the transfer or pern'iutator relay K.

The relay 0 operates and, at 110, cuts the circuit of the relays of the switching mechanism. The latter returns to normal. At this moment the relay J comes likewise to normal, since lis of C1 is .interrupted.

lVhen J comes to normal, K has its circuit closed by 42 and is energized; through 413 it causes the energization of the relay K and renders relay 0 inoperative. The relay K is maintained operative by its contact 76.

The entire switching mechanism assemblage is thus in the position which it occupied betore receiving the first series of impulses, but with this difference that, P, K, and K being energized, the. lines LA, LB, LC, Ll) are respective] y connected, with lines N1, N2, N3, N4.

The coupling operation, the re-setting to zero and the transfer take place very rapidly while the caller prepares his second ligit, on numeral 1, by carrying the latter (1) ot the. wheel BC in front of the arrow F.

In its return movement the wheel RI opens the contact 11 once; '2: returns to normal; Mn receiving an impulse, relays C1 and J are excited. The line LE, through contact 11?) of C1 in operation, back contact 114 of G2 at rest, line IA and front contact 79 of K in operation, will. be connected with N1.

After the single imymlse corresponding to the tigure 1, the contact 10 of the call dial will again be closed and will short circuit the test relay T, causing the simultaneous excitation of relays and. I. The line LE is then connected to negative of the trout contacts 39 and 10 in operation, but this negative is given directly to the line N1, the resistance ill being short oircuited by the contact 74; of K.

The line N1 being connected to negative, as explained, and the coupler relay of group CGA being energized, the selective line LS of station C1 is connected to negative. As a consequence the coupling relay OP of station C1 is energized.

The action of the switching mechanism, controlled by the call dial (it the caller, thus has resulted in actuating the coupling relay C P ot the called station C1. The selection is thus complete.

After the last impulse the relays I, J and K are energized and the control relay L has its circuit closed by the contacts 73, 4-1 and 75. he relay L operates and, through its contact 4-5, closes the circuit of the prezero relay PZ, which position is maintained by its contact 26 and which, at 65, partially of the relays of line CR1.

closes the circuit of the general zero relay 2. The result is that when the calling station is cut off from the line L1, as set forth hereinafter, the relays 'i and Vi return to normal; contact 71 at rest actuates Z; the latter breaks'the circuits of the commutator, either directly by means of its contacts 77 and 48, or by controlling the relay of the commutator by means of its Contact 47. It is to be noted that the retaining contact 46 of PZ is fed at the same timeby the contact 42 of J and the contact 129 of ARM, in order thattheresetting to zero of the commutator controlled by 14 be assured.

(1)). Calling a, free station and answer thereof.

The action of the call dial of station A4 having resulted in passing current through the selective line LS of station C1, the connecting relay CP of this station operates and, through its contact- 14, connects to a pole of the battery the operating coils 21 of the relays F of station C1 over the three connecting lines (CR1, CR2, CR3).

But it will be noted that only the signal relay G1 of the connecting line CR1 is connected to the other pole of the battery, this relay G1 being in series with the coils 21 The result is that only the relay F of G1 on the line CR1 functions and, thru its contacts 26, connects the line from the station A4 over the wires C1 C2, fori'ning the connection CR1. The signal relay G1, in series with the relay l of C1, likewise operates and connects the connecting line over the lines Al A2, connected with the call vibrator. Contact 28 of relay G1 being closed, relay U operates and, through its contact 117, actuates the vibrator. The call is thus made through the lines A1 A2 C1 C2 to the station Chthc alarm thereof being sounded.

The relay U, through its contact 115, has closed the circuit of the call mechanism or train MA; the corethereof rises and closes the contact 53, which causes the energization of the relay M1; the latter is held at 93 and, at 94, breaks the circuit of the mechanism MA; the core thereof then descends slowly. This mechanism regulated so that its core can close the contact 58 only after a minutes time, for example. Under these conditions the duration of the call, will be one minute, as explained hereinafter.

The station C1 should answer before-the end of this minute by unhooking its receiver.

At the moment of connecting G1 on the line, the contact of CP being open, the winding of the'feed relay D, connected to positive, has had its short circuit broken, while the other winding of D is connected to negative by the contact 13 of the relay F. Theresult is that when station C1 un- 8 I 1,ao5,773-

hooks its receiver the feed relay Dof this station operates and is maintained in opera: tion by its contact 18 until the subscriber hooks up. 7

The relay D, through its contact 15 and through the contact 23 of relay F of G1 on the line CR1, feeds the retaining coil 22 of the relay F, and at the same time the relay H1 in series therewith.

Through its contact 17, the relay D shifts the line LS to the line PL, which brings GP to the position of rest. The operating coil 21 of F is no longer traversed by current and the relay G1 comes to rest, but the relay F of G1 on. the first connecting line CR1 remains energized, since its re taming coil 22 is traversed by current, as hereinafter explained.

The line LS of C1 being shifted on the line PL by the contact 17 of D, the line PL is supplied with current; since, at this moment, the train or mechanism has not yet arrived at the end of its travel the tirst operating relay M1 is constantly energized. The result is that, through 95 at rest, the reply relay R is energized. At 120, this cuts the relay U; the vibrator is stopped and M1 comes to rest, 115 being open. The relay R has a retaining contact 119 fed by the line PL. It is excited when this line is traversed by current and holds the con tact 121 open, which prevents energization of relays X and TV by PL and contact 95 at rest.

The line PL being connected with the line CA, the latter is placed under current and, through the contact 16 of the relay A of A4, the electro CP of A4 is excited. The latter, through its contacts 14, actuates the relay F of A4 on the connecting line CR1, since only the latter is connected to the other pole of the battery. But since at this moment A4 is unhooked, its feed relay D functions and, through 15, feeds the. retaining coil 22 of its relay F on CR1.

In functioning, the feed relay D of the station, through its contact 15, has broken the circuit of its call relay A. The latter comes to rest and cuts the station A4 from the commutator COP at relays I, 11 and i return to normal; this latter, through 71, actuates the general zero relay Z. The commutator being in the inoperative state, line PL is no longer fed, and the reply relay R no longer energized.

It is thus seen that the call instruments and the con'nnutator are released immediately after the response, without awaiting the end of the travel of the mechanism MA, which forms an important improvement for the whole, when it is considered that a telephonic response is often obtained in a few seconds.

The relay U, in parallel on the relay U, like the latter, has had its circuit broken too llU

during the action of the reply relay R. However, the relay U does not come to rest immediately; its action is different in that all the apparatus of the commutator and the call elements are made inoperative before the closure of 122, although at this moment the coil 32 of the transfer member of connecting line PHl is fed by 34, 29 of H1, 122 of U, 118 of U and 54 of X. PHl functions and is maintained in operation by its contact 34 and the contact 30 of H1; contact 36 comes into position of operation and, the positive pole of the battery is passed to contact 36 of PH2, that is, to connecting line CR2, which is the line utilized for a new call.

It is to be noted that the line transfer or change is effected automatically, without )ecial regulation of the relays.

Finally, the relay U, through its contact 123, keeps Q energized until the stations have been connected and so as to prevent a call coming in during said connection.

The two stations A4 and C1 are thus engaged in conversation. They are connected through the condensers UR by the line CR1 and fed respectively by their feed relays D. These latter, through their contact 15, maintain energized the coils 22 of the electros F and the connecting line electro H1, the latter keeping energized, through 30, the transfer relay of connecting line PHl.

' lVhen one of the stations hooks up its feed relay D and its relay F come to rest. \Vhen both stations have hooked up the relay H1 comes to rest, and also the electro IHl. The line CR1 is again available.

It is to be noted that the relay PHl is provided with a locking contact 38, cont-rolling its winding The result is that, through the line L3, the winding 33 is energized if Q functions, that is to say, if another call comes to the switchboard during the course of the conversation, so that PHl may not be released during the call, even if the busy stations have hooked up.

(0) Calling a station and receiving no U/TlS'IUGT.

It is assumed that station A4 calls station C1. but the latter, although free, does not answer.

The operation is the same as precedingly set forth for an ordinary call. up to the momentof the action of the mechanism MA. and the call vibrator ViB.

The vibrator operates and the alarm of station C1 sounds during all the time in which the core of MA descends (one minute, for example). Coming to the end of its travel, the core of MA closes the contact 58 which, through back contact 98 of M2 at rest and front contact 96 of M1 in operation, excites relays X and V.

Relay V. through its contacts 55, interposes a potentiometer between lines Al A2 and the vibrator, so as to reduce the call current sent over this line.

The relay X, in operation, is maintained so by its contact and by the contact 116 of U. Contact 54 of X, being in operation, established a circuit for the relay G1, passing through the contact 27 of G1 and the resistance R1. The result is that G1 remains energized and keeps up the call on the line, even if the relay CP of station Cl called comes to rest, as will be explained.

Summarizing: At the end of the first travel corresponding to the call, the mechanism sends over the line CR1 a current which is weaker than the call current.

But, through its contact 57, X has again closed the circuit of the mechanism MA, which had been opened at 94 by MI. The core of the latter rises and closes the contact 53. Since, at this moment, X is energized, the second position relay M2 operates, its circuit being closed at 53 and 57.

M2 operating, is maintained thus by its contact 97 and, at 24, breaks the circuit of the mechanism MA; the core of the latter descends slowly.

At 19, M2 breaks the circuit of M1 and the latter comes to rest. Contact 95, coming to rest, connects the line PL t0 the entrance of X, whereby the latter receives current through the contact 52 and the contact 116 of U.

Line PL being traversed by current, line CA is also traversed by current and, through contact 16 of the call relay A of A4, the relay CP of A4 is energized and thus actuates the relay F of A4 on the first connecting line CR1. A4 is thus connected on the line CR1 from which it receives the weak signal current coming from the potentiometer. The result is a sound in the receiver of station A4, this being the signal for No answer.

But, since CP and F of A4 have operated, the feed relay D of A4 receives current, 20

' of CP being open and 13 of F closed. This relay D functions, is maintained in function at 18 and, at 15, cuts the circuit of the call electro A. The latter, at 60, breaks the connection of A4 with the commutator, the latter coming to rest at the same time as the coupling relay CI of C1.

The relay D of A4 having .tuctioned, A being no longer energized. CP of A4 comes to rest; however, the relay F of A4 remains energized, through its maintaining coil. 22, controlled by 15 of D and the contact 23.

Although CP of station A4 is no longer energized, the signal relay G1 does remain energized since, first, it is maintained so by its own contact 27, resistance R1 and contact 54 of X, and, further, it has a second locking circuit thru 31 of H1, the resistance R1 and the contact 54 of X.

Consequently the receiver of station A4 gets the signal of No answer, relay G1 retained so by the contact'18.

maintaining the connection of the line CR1 with lines A1 A2.

Shortly after the beginning of its descent, the mechanism MA closes its contact 59, which causes the energization of M3, contact 19 M2 being operative. M3 acts and its act-ion is maintained by its contact 126, and at the same time, at 125, it breaks the first- .niaintenance circuit of the signal relay G1.

However, this latter remains operative through its second maintenance circuit-, passing through 31 of H1.

Two conditions may then be present: The subscriberof station A4, receiving the No answer signal, hooks up before the end of the second'travel of MA, or does not hook up.

In the first case, when the subscriber hooks up, the feed relay D of A4 has its circuit broken; it comes to rest, releasing F and H1 the latter comes to rest and, at 31, breaks the circuit .of G1, which likewise comes to rest and, at 28, breaks the circuit of U.

U, being no longer energized, stops the action of the vibrator and cuts the circuits of M2 and V; relay M3 also comes to rest. All the call elements are thus at rest. Relay U being different, opens an instant after contact 123,'Q is no longer energized and the switchboard is ready for a new call.

If the subscriber at station A4, although receiving the No answer signal, does not hook up before the end of the second travel of the mechanism MA, the latter, at the end i of its travel, closes the contact 58 which, thru front contact 98 of M2 in operation, causes the excitation of the line cutting relay CD. The latter, through its contacts 124, breaks the circuit of the relay H1 and, hence, through its contacts 124, the circuit of the maintenance coil 22 of F of station A4, which is thus cut out of the line. However, its feed relay D remains excited, since it is It is apparent that a line cannot be isolated by failing to-hook upI Relay D of A4 simply remains energized until A4 hooks up, but the line CR1 is free.

lVhen CD, at 124, has cut the circuit of H1, the latter, at 31, has cut the mainte nance circuit of G1. The latter comes to rest; 28 is open; U is no longer excited and breaks the circuit of a ll the call elements; an instant afterward U comes to rest and frees the switchboard.

((1) Calling a busy station.

Station A4 calls station G1 which is busy, being in conversation, for example, on the line (3R1.

Station A4 is connected with the switching mechanism COP through its call relay A. By controlling the commutator through its call dial, the station A4 causes current to pass through the selective line LS of station C1.

1 e as r 2 But, station C1 being busy, its feed relay is operative and, through the contact 17, the

line LS, is shifted on the line PL, current thus traversing the latter. As, at this moment the relay M1 is at rest, the mechanism MA, not yet having functioned, line PL, through contact 95 at rest, feeds relays X and V. The potentiometer is thus interposed on the call line A1 A2.

Line PL, being traversed by current, feeds line CA. The'latter, through contact 16 of call relay A of A4, feeds relay GP of A4, which functions and actua the relay F of A4 over the second connecting line CR2, since the first is busy with conversation of station C1.

The signal relay G2 functions at the same time as F and connects the call line on the second line CR2 thru the contacts 25.

The relay. G2 is n'iaintained operative through its contact 27, the resistance R1 and 54 of X, in operation.

During the operation of the relays CP and F of A4, the relay D of this station has been energized. Through 15 of D and 23 of F the coil 22 of the latter has been placed under current at the same time asthe relay H2.

The relay D, in operation, has broken, at 15, the circuit of the relay A which, at 60, isolates the station A4 from the COlilll'iUttItOl, the relays 2', z" and I of which come to rest, which actuates the zero relay Z and brings the commutator to Zero.

The relay G2 closes the contact 28 during its operation, which actuates U and, hence causes the operation of the vibrator and the mechanism, the potentiometer being interposed on the call circuit.

When the call mechanism A, at the top of its travel, closes the contact 53, the relay M2 fnnctions, since X is energized. M2 is maintained operative by its contact 97, Ml beingbroken at 19.

The weak call current is thus sent over the line and station A4, getting it in its receiver,,is informed that station C1 is busy. This is effected in the order set forth above when a No answer signal is sent. However. station A4 may easily determine whether the signal is No answer or Busy, as it does not receive the former until at the end of a certain time, that is, after the first travel of the mechanism MA, while it receives the second immediately after giving the number of the called station.

W z'zh zf/w'cc connecting Zines busy.

hen the three connecting lines are busy the three relays PHl, 1 1-12, PHZB, are excited. The result is that, through the contacts 36, relay AC isexcited' and, at 78, closes the circuit of relay Q, which, controlling relays Q1, Q2, Q3, etc. prevents any call coming to the switchboard. The stations are prov d d fe u eon ti n, the r testr ys T L gs tit)

not being energized when the subscriber unhooks. However, at 57, relay AC breaks the line L3, so that the PH relays can not be maintained operative and the switchboard made ready for a new call as soon as a line becomes free, that is, as soon as a relay PH, being no longer energized, drops its contact 36, which cuts oil the feed of AC.

(6) Faults.

The operative errors which may be made by a station are tive in number:

1. A station unhooks its receiver, makes no call and again hook up.

2. A station unhooks its receiver, makes a partial call and again hooks u).

3. A station unhooks its receiver, makes no call and doesnot hook up again.

i. A stat-ion unhooks its receiver, makes a partial call and does not hook up again.

5. A station unhooks its receiver and calls a number higher than the numbers of the stations comprising the system.

In all cases the commutator should be brought to rest and, in the three latter only, the station must be informed that an error has been made.

At the moment in which a calling station is connected on the line L1, coming to the commutator COP, relays a and 2" operate. Contact 89 being closed, the relay FA is energized and maintained excitedly by its contact 84.

The electro FA, through its contact 85, causes the excitation of the faulty mechanism MF. The core of the latter rises and raises the contact 82, which closes the circuit of relay F13.

Relay FB, at 83, breaks the circuit of the mechanism MF, whose core descends slowly. The duration of this descent isregulated so as to permit the caller to get his number before closure of contact 80.

Relay FB is kept operative by its contact 83 and contact 85 of FA, while the latter is energized; the result is that it the caller unhooks without dialing the number, 2' remains excited, as also FA and Fl). The mechanism MF arriving at the end of its travel closes the contact 80 which, through 86 of FC and 88 0t '11, actuates relays X and \V and, hence, sends out a signal o'l. reduced intensity. These operations take place as explained above under No answer.

At the same time, by means of the contact 80 in operation and contact 92 of FC at rest, the relay PZ is excited and actuates Z which brings the commutator to rest.

It is thus seen that when a station unhooks and does not call, the commutator is rendered inoperative, the station being informed that an error has been made.

If the station makes but a partial call, the relay FA. is energized at each impulse and at each time actuates the mechanism MF. After the partial call, it the station has not again hooked up, the mechanism continues its travel, closes the contact 80, renders the commutator inoperative and interms the station that error has been made.

If, after an error, the station has hooked up before closure of contact 80, relay 2' comes to rest, 88 is not closed. Consequently, X and TV a re not energized during the closing of 80. P71 only will operate to bring the commutator to normal.

It, 011 the contrary, the call \Vt s made normally, the relay L, operating after the normal act-ion ot the commutator, would have. closed the circuit of relay Ft] at 4-5. latter, maintained by its contact 87 and, at 86 and 92, breaks the circuits controlled by 80. The closure of this latter is then without result.

VJ hen a station calls a number higher than the numbers of the stations of which the system is comprised, the result is either the excitation of relay CG5 or of relay G5 on the commutator. These two relays, through their contact and contact 81 of L, actuate the relays X and V and, consequently, send an error signal to the calling post, the commutator being brought to the position ct rest, as in the case of a normal call.

It is apparent from what has been set forth that the assemblage of this error arrangement assures complete protection against mistakes of operation.

The application is directed solely to the.

process utilized for assuring communication of different stations of a system, and does not relate to the construction of a tel-ephonio circuit between two stations or posts, which may be varied according to conditions, but which may be made the subject of another application for patent as relatingto the above process and requiring fundamental changes of construction.

Having thus described the invention, what is claimed is:

1. In an automatic telephone system for effecting connection between a plurality of stations, the combination of a controlling system comprising a. selector, a pair of relays adapted to respond to impulses ot ditl'erent intensity, said selector comprising a plurality of relays so connected that each relay oi? said selector controls the circuit of the relay following, said relays being divided into two series of relays and connected respectively to two lines, acoupling relay, whereby upon an impulse actuating one of the relays ot the first named pair of relays certain relays ot the selector are actuated to energize said. coupling relay to effect the coupling of the stations with a connecting line, auxiliary means to effect the call, and to effect a special signal if not available, and means in case of The fault to ellect the return to normal of said system, and the emission of a signal indicating the fault.

2. A telephone system as set forth in claim 1 having a call relay for each station, said dial when said selector is engaged and a plurality of quick breaking relays adapted to actuate a contact in said line and actuated by said selector at the beginning of a call and maintained in action during the calling oper ation.

a. In a telephone system for ellecting con nection between a plurality of stations, divided into two groups each selected by a number composed of two digits, the first digit characterizing the group and the second the line and having a calling method based upon the transmission of impulses of two types differentiated by the strength of current, impulses of one type selecting the digits forming the number of the called station and an impulse of the other type indieating the end of said digit, the combination of a controlling system comprising an impulse relay, a final relay, a call dial for each station, a call. relay for each station, the coils of said impulse relay and said final relay being in series in a circuit connected bysaid call relay of the calling station to the line of the station, said impulse relay being adapted to res nd to impulses of said lirst type and said mal relay being adapted to respond to impulses of said second tyie, a selector comprising a plurality o relays adapted to respond to currents of different intensity, and so connected that each relay controls the circuit of the relay following, said relays being divided into two groups in series and connected respectively to two lines, a coupling relay, whereby upon an impulse actuating one of the relays oi the first named pair of relays, certain relays of the selector are actuated to energize said coupling relay to effect the coupling of the stations witha connecting line, auxiliary means to effect the call, and to effect a special signal if not available, and means in case of fault to etfcct the return to normal of said system, and. the emission ofa signal indicating the fault.

In an automatic telephone system for effecting communication between a plurality of stations, the combination of a controlling system comprising a selector having a plurality of relays so connected that each re lay controls the circuit of the relay following, said relays being divided into two series,a pair of relays adapted to respond to impulses of different intensity, a working relay, odd and even lines, said series relays being connected respectively to said odd and even lines, electrical relay means associated with said selector and said working relay for preventing two relays of said selector from being excited by the same impulses, a coupling relay, whereby upon an impulse actuating one of the relays of the first named pair of relays certain relays of the selector are actuated to energize said coupling relay to effect the coupling of the stations with a connecting line, auxiliary means to effect the call, and to effect a special signal if not available, and means in case of fault to eli'ect the return to normal of said system, and the emission of a signal indicating the fault.

6. In an automatic telephone system as set forth in claim 1 for effecting communication between a plurality of stations, the combination of a selector, comprising a plurality o'l' relays, an impulse relay, a final relay, a call dial for each station, a coupling relay at each station, said coupling relay supplied with current through a selecting line for efiecting the junction of the line of such station with the conversation line, a group connecting relay at each group station to effect the connecting of the selecting lines of said group station with circuits selected by said selector, said group connecting relays adapted to be connected with said circuits during the first series of impulses, a locking circuit having a pilot relay to ell'ect the return of the selector to its normal position after the first'series of impulses, and a shifting relay to effect the supplying of said selective line with current from a selected circuit at the end of the second so 'ics of impulses.

7. An automatic telephone system as set forth in claim v1 having a plug relay at each station in each connecting line to eil'ect the connecting of each of two corresponding stations and adapted to be controlled by the coupling relay of the corresponding station, a signal relay in the working circuit of said plug relay to effect the calling and signalling members and the connecting with the signal line, a change over relay for each link, a locking circuit associated with said plug relays and having a relay in said circuits, said change over relay being controlled by said locking circuit and the calling me1nher after said members have acted, contacts associated with said change over relays to effect the transferring of current of the working circuits of the plug relays from its link to the working circuits of the plug relays of the link following, a locking winding on said change over relay to prevent the liberation of the link during the call, and an auxiliary link relay adapted to be controlled by said relays controlling the change over of said links and arranged to break the cir cuits of the calling relay at all stations When the links are engaged.

S. In an automatic telephone system as set forth in claim 1, means for sending the calling signal, the not available signal and the no reply signal comprising a first position relay, a second position relay and a retarding relay cooperating with said relays for controlling the duration of the signal and adapted if said first position relay operates at the same time said retarding relay operates, to send the call current over the signal line during the time of operation of said retarding relay, and adapted if said second position relay operates at the same time said retarding relay operates, to send a signal if not available over the signal line, a reply relay associated with the said calling members to effect the arrest of the calling members when the called station replies, and a disconnecting relay controlled by the retarded relay and the second position relay and adapted to re lease the connecting line on which the signal current has been passed at the termination of said signal.

9. In an automatic telephone system as set forth in claim 1, a feed relay at each station, the coils of said feed relay being energized by the feed current of the station and adapted to control a current maintaining the connection between the station line and the link employed for conversation, and connecting the selection line of the station to a busy back line when the call station is engaged in order to control the coupling of the line of the calling station With a free link.

10. In an automatic telephone system as set forth in claim l, a retarding relay adapted to be energized at the beginning of a call and adapted to control the action of the call dial, whereby at the end of its travel, if the number given incomplete to send a signal to the station giving the Wrong nu1nher and release the elements fixed in position by the erroneous call, and supplementary relay means associated With the selector relays to effect the sending of a signal to a station requesting a number higher than the highest number of the system and to effect the restoring to normal of the mechanism operated by the requesting of the erroneous call.

In testimony whereof I hereunto afiix my signature.

LOUIS LUCIEN EUGENE CHAUVEAU. 

